1. Field of the Invention
This invention relates generally to conductive polymers. It relates particularly to aromatic condensation polyimide films and coatings which have surface conductivities in the range of 1.7.times.10.sup.-3 to 4.5 .OMEGA..sup.-1, and to the process for their preparation.
2. Description of the Related Art
The incorporation of metal salts and complexes has been used as a means of providing polyimides with increased bulk conductivities and/or greatly enhanced surface conductivities. Additives of numerous metals including platinum, palladium, copper, cobalt, gold and silver have been investigated. (L. T. Taylor, et al, U.S. Pat. No. 4,311,615(1982) and L. T. Taylor, V. C. Carver, T. A. Furtsch, "Incorporation of Metal Ions into Polyimides," ACS Symposium Series. No. 121 Modification of Polymers, C. E. Carraher, Jr., and M. Tsuda, Eds., pp 71-82, 1980.)
Polyimides with metallized silver surfaces have been reported with the addition of silver acetate and silver nitrate to the polyamic acid resin (A. L. Endrey and E. I. DuPont De Nemours and Co., U.S. Pat. No. 3,073,784 (1963) and A. Auerbach, J. Electrochem. Soc., p. 937, April 1984.). Conductive surfaces were achieved after extended cure times or a high temperature (360.degree. C.-370.degree. C.) bake under a blanket of carbon powder. In addition to the incorporation of silver acetate or nitrate into polyamic acid resins as an approach to achieving conductive polyimides, counter-current diffusion has also been successfully used to provide polyimide films with conductive and reflective metallic interlayers (L. E. Manring, Polymer Communications, 28, 68, March 1987.) Conductive polymer films have also been reported by infusion deposition of silver and compounds into films of polyphenylquinoxaline and several other high temperature polymers although polyimides were not among them (R. Liepins et al, U.S. Pat. No. 4,876,032(1989.)
A primary object of the present invention is to provide aromatic condensation polyimide films and coatings that have surface conductivities in the range of 1.7.times.10.sup.-3 -4.5.OMEGA..sup.-1.
Another object of the present invention is to provide a process for increasing the conductivity of an aromatic condensation polyimide to a range useful for the electronics industry.